The present world context regarding the exploitation of an electrical energy transmission network is the following: ageing components, increasing demand for energy, deregulation and opening of markets, increasing pressure by clients for quality and reliable energy. The electrical utilities are therefore required to know precisely the state of their transmission network in order to apply the principles of preventive maintenance for safekeeping the reliability of the systems. The evaluation of the state of a component is evaluated, inter alia, through measurements by means of sensors. With regard to the gathering of information, numerous sensors have been developed but the positioning of these sensors, in order to access the components, often remains an important challenge. The use of remote-controlled vehicles (ROV) for this task in order to achieve the inspection of circuits of conductors is therefore very appropriate.
Many vehicles of the ROV type have been developed in the past. A quick overview will bring to the fore the characteristics and disadvantages of the main ones.
Referring to FIG. 1, there is shown a remote-controlled line chariot for the inspection of circuits with a simple conductor and which is the object of U.S. Pat. No. 6,494,141 (MONTAMBAULT et al.) This remote-controlled vehicle is very efficient, compact, relatively light and easy to use. It also has a good traction force which renders it very versatile. It is a third generation prototype that has proven many times over its efficiency, its mechanical robustness and its robustness to work under live electrical conditions (315 kV, 1000 A). It allows the de-icing of overhead ground wires and of conductors, thermographic and visual inspections and the measurement of the electrical resistance of joints. It travels on simple conductors regardless of their diameters. However, this type of ROV is only capable to pass over mid-span tension joints, but cannot pass over on its own pylons or vibration dampers or spacers. It has to be dismantled when it reaches an insurmountable object and has to be put back together again on the other side of the obstacle.
Referring to FIGS. 4 and 5, there are shown different chariots used for the evaluation of a level of corrosion in steel cables or that allow to carry out the method of “pulleys-cradles”. FIG. 4 shows a chariot commercialized by the firm Furukawa. FIG. 5 shows another similar chariot made by the firm Fujikura. These chariots use old technologies. In fact, the chariots use two wheels with a motor. They have a very low traction force. They cannot work with under live electrical conditions. They travel on a simple conductor, without being able to pass over pylons or spacers.
Referring to FIG. 6, there is shown a robot for installing warning markers. It is a voluminous and heavy prototype. It is dedicated to the installation of warning markers on overhead ground cables (in general).
The above-mentioned concepts may sometimes be efficient for certain precise tasks but are often heavy, sometimes fragile and may rarely work under live electrical conditions. However, the principal disadvantage of these concepts is their inability to pass over obstacles that are located on the conductors, such as vibration dampers, and even less to change spans by passing over the elements which hold the conductor to each pylon. They are therefore all restricted to intervene only between two pylons or to be removed and then reinstalled on the other side of the insulator strings by a human operator. One can therefore easily imagine the advantage of providing an ROV concept that could be used on many spans to inspect, for example, several kilometers of conductors without requiring direct human intervention.
Other concepts, having in particular the same object, have however been developed. Indeed, below, there are described some experimental prototypes for passing over obstacles on simple conductors.
Referring to FIGS. 2 and 3, there is shown prototypes or concepts that can travel on a simple conductor and can pass over pylons (insulator strings and vibration dampers). FIG. 2 shows a prototype by the firm TVA (Tennessee Valley Authority). FIG. 3 shows another prototype by NSI-NASA (Sewada et al.) These apparatus are very large, very complex and difficult to install. It is not clear if they are able to work under live electrical conditions. It seems that these apparatus were not developed in consultation with the eventual users because they are much too large and complex to be usable in a network in a reliable manner. The speed of passing over the obstacles is not fast, because of the complexity of the mechanisms that are used. The price of these apparatus is possibly disadvantageous because of the complexity of the systems.
Referring to FIGS. 7 and 8, there is shown respectively a motorized aerial basket (Hydro-Quebec TransEnergie) and one that is non-motorized (Italy). These prototypes are not vehicles of the ROV type because they are used to transport linemen as they are mounted on conductors. These concepts allow them to move on the conductor bundles and to pass over the spacers and pylons (insulator strings). The mounted operator must then activate levers and to deploy on his own certain supplementary wheels in order to have enough support on each side of the obstacles. The operation requires a relatively long time.